Any other mailbox, over IMAP and SMTP. Same as Gmail or Outlook once it is connected: Selda sends as you and replies land back here.
Any IMAP/SMTP mailbox
Send from your own address
Replies in your inbox
Selda sends from this mailbox under your own name and follows the threads it starts. Those replies appear in the Selda inbox; the rest of your mail is not shown there.
All plans.